Replace kube-lego docs with cert-manager (#7659)
Replace kube-lego docs with cert-manager (#7659)

Since kube-lego has not been maintained in quite a while,
I thought it would be best to remove the documentation about it
and replace it with information about cert-manager.
kubernetes/ingress-nginx,canhnt/ingress,kubernetes/ingress-nginx,canhnt/ingress,kubernetes/ingress-nginx,kubernetes/ingress-nginx,canhnt/ingress,canhnt/ingress,kubernetes/ingress-nginx